Problem 3.306

A plane spiral with a great number \(N\) of turns wound tightly to one another is located in a uniform magnetic field perpendicular to the spiral's plane. The outside radius of the spiral's turns is equal to \(a\). The magnetic induction varies with time as \(B=B_{0} \sin \omega t,\) where \(B_{0}\) and \(\omega\) are constants. Find the amplitude of emf induced in the spiral.